| Existing and emerging layer-4 switching technologies require packet classication to be performed on more than one header elds, known as layer-4 lookup. Currently, the fastest general layer-4 lookup scheme delivers a throughput of 1 Million Lookups Per Second (MLPS), far o from 25/75 MLPS needed to support 50/150 Gbps layer4 router. We propose the use of route caching to speed up layer-4 lookup, and design and implement a cache architecture for this purpose. We investigated the locality behavior of the Interent trac (at layer-4) and proposed a near-LRU algorithm that best harness this behavior. In implementation, to best approximate fully-associative nearLRU using relatively inexpensive set-associative hardware, we invented a dynamic set-associative scheme that exploits the nice properties of N-universal hash functions. The cache architecture achieves a high and stable hit ratio above 90 percent and a fast throughput up to 75 MLPS at a reasonable cost ($700/1700 for 50/150 Gbps rou...

Provision of QoS-related router functions such as traffic regulation, policy routing, and usage-based accounting requires that a flow table stores state information for active flows. The design of such a flow table is not trivial for a high-speed Internet router (e.g., 100+ Gbps) with a large number of active flows (e.g., tens of millions) and a high packet arrival rate (e.g., tens of millions of packets per second). Targeting two different models (centralized and distributed) of router design, we propose a software-based design to be implemented on individual line cards, which is suitable for the distributed model, and a hardware-based design to be implemented in the main forwarding engine of a router, which is suitable for the centralized model. The software-based design, adapted from hash table data structure, employs a practical and effective technique to solve the garbage collection problem caused by the expired flows. The hardware-based design, adapted from the architecture of an N-way set-associative cache, employs a dynamic set-associative scheme to reduce the overflow ratio that traditional set-associative scheme incurs, by a high percentage, and a pipelined design to achieve a throughput of 100+ Gbps. The performance evaluation results from both trace-driven simulation and statistical analysis demonstrate that both designs are cost-effective for their targeted router models.